Synthesis and Biological Activity of N4-Methyl-5-azacytidines

Abstract

Protected N4-methyl and N4,N4-dimethyl derivatives of 5-azacytidine 3 and 4 were prepared by selective aminolysis of benzoylated 4-methoxy-1-(β-D-ribofuranosyl)-1,3,5-triazin-2(1H)-one 5, by glycosylation of silylated N4-methyl- or N4,N4-dimethyl-5-azacytosines 7 and 8 with 2,3,5-tri-O-benzoyl-α,β-D-ribofuranosyl chloride (11) or by several modifications of the isocyanate method. By the isocyanate approach, also the α-D anomer of protected N4-methyl-5-azacytidine 17 was obtained as a minor product. The protected dimethyl derivative 4 was also obtained by the reaction of isobiuret 22 with dimethylformamide dimethyl acetal. The free nucleosides 1 and 2 were obtained either by aminolysis of the free methoxy nucleoside 23 with methylamine or dimethylamine, respectively, or by methanolysis or ammonolysis of the corresponding benzoyl derivatives 3 and 4. The free α-D anomer 24 was obtained by methanolysis of its tribenzoate 17. Nucleosides 1 and 2 exhibited a lower antibacterial, antitumor and antiviral activity than the unsubstituted 5-azacytidine.